The present invention relates to a steerable rotary drilling device and a method for directional drilling using a rotary drilling string. Further, the present invention relates to a drilling direction control device and a method for controlling the direction of rotary drilling.
Directional drilling involves varying or controlling the direction of a wellbore as it is being drilled. Usually the goal of directional drilling is to reach or maintain a position within a target subterranean destination or formation with the drilling string. For instance, the drilling direction may be controlled to direct the wellbore towards a desired target destination, to control the wellbore horizontally to maintain it within a desired payzone or to correct for unwanted or undesired deviations from a desired or predetermined path.
Thus, directional drilling may be defined as deflection of a wellbore along a predetermined or desired path in order to reach or intersect with, or to maintain a position within, a specific subterranean formation or target. The predetermined path typically includes a depth where initial deflection occurs and a schedule of desired deviation angles and directions over the remainder of the wellbore. Thus, deflection is a change in the direction of the wellbore from the current wellbore path.
It is often necessary to adjust the direction of the wellbore frequently while directional drilling, either to acconmmodate a planned change in direction or to compensate for unintended or unwanted deflection of the wellbore. Unwanted deflection may result from a variety of actors, including the characteristics of the formation being drilled, the makeup of the bottomhole drilling assembly and the manner in which the wellbore is being drilled.
Deflection is measured as an amount of deviation of the wellbore from the current wellbore path and is expressed as a deviation angle or hole angle. Commonly, the initial wellbore path is in a vertical direction. Thus, initial deflection often signifies a point at which the wellbore has deflected off vertical. As a result, deviation is commonly expressed as an angle in degrees from the vertical.
Various techniques may be used for directional drilling. First, the drilling bit may be rotated by a downhole motor which is powered by the circulation of fluid supplied from the surface. This technique, sometimes called xe2x80x9csliding drillingxe2x80x9d, is typically used in directional drilling to effect a change in direction of the a wellbore, such as the building of an angle of deflection. However, various problems are often encountered with sliding drilling.
For instance, sliding drilling typically involves the use of specialized equipment in addition to the downhole drilling motor, including bent subs or motor housings, steering tools and nonmagnetic drill string components. As well, the downhole motor tends to be subject to wear given the traditional, elastomer motor power section. Furthermore, since the drilling string is not rotated during sliding drilling, it is prone to sticking in the wellbore, particularly as the angle of deflection of the wellbore from the vertical increases, resulting in reduced rates of penetration of the drilling bit. Other traditional problems related to sliding drilling include stick-slip, whirling, differential sticking and drag problems. For these reasons, and due to the relatively high cost of sliding drilling, this technique is not typically used in directional drilling except where a change in direction is to be effected.
Second, directional drilling may be accomplished by rotating the entire drilling string from the surface, which in turn rotates a drilling bit connected to the end of the drilling string. More specifically, in rotary drilling, the bottomhole assembly, including the drilling bit, is connected to the drilling string which is rotatably driven from the surface. This technique is relatively inexpensive because the use of specialized equipment such as downhole drilling motors can usually be kept to a minimum. In addition, traditional problems related to sliding drilling, as discussed above, are often reduced. The rate of penetration of the drilling bit tends to be greater, while the wear of the drilling bit and casing are often reduced.
However, rotary drilling tends to provide relatively limited control over the direction or orientation of the resulting wellbore as compared to sliding drilling, particularly in extended-reach wells. Thus rotary drilling has tended to be largely used for non-directional drilling or directional drilling where no change in direction is required or intended.
Third, a combination of rotary and sliding drilling may be performed. Rotary drilling will typically be performed until such time that a variation or change in the direction of the wellbore is desired. The rotation of the drilling string is typically stopped and sliding drilling, through use of the downhole motor, is commenced. Although the use of a combination of sliding and rotary drilling may permit satisfactory control over the direction of the wellbore, the problems and disadvantages associated with sliding drilling are still encountered.
Some attempts have been made in the prior art to address these problems. Specifically, attempts have been made to provide a steerable rotary drilling apparatus or system for use in directional drilling. However, none of these attempts have provided a fully satisfactory solution.
United Kingdom Patent No. GB 2,172,324 issued Jul. 20, 1988 to Cambridge Radiation Technology Limited (xe2x80x9cCambridgexe2x80x9d) utilizes a control module comprising a casing having a bearing at each end thereof for supporting the drive shaft as it passes through the casing. Further, the control module is comprised of four flexible enclosures in the form of bags located in the annular space between the drilling string and the casing to serve as an actuator. The bags actuate or control the direction of drilling by applying a radial force to the drive shaft within the casing such that the drive shaft is displaced laterally between the bearings to provide a desired curvature of the drive shaft. Specifically, hydraulic fluid is selectively conducted to the bags by a pump to apply the desired radial force to the drilling string.
Thus, the direction of the radial force applied by the bags to deflect the drive shaft is controlled by controlling the application of the hydraulic pressure from the pump to the bags. Specifically, one or two adjacent bags are individually fully pressurized and the two remaining bags are depressurized. As a result, the drive shaft is deflected and produces a curvature between the bearings at the opposing ends of the casing of the control module. This controlled curvature controls the drilling direction.
United Kingdom Patent No. GB 2,172,325 issued Jul. 20, 1988 to Cambridge and United Kingdom Patent No. GB 2,177,738 issued Aug. 3, 1988 to Cambridge describe the use of flexible enclosures in the form of bags in a similar manner to accomplish the same purpose. Specifically, the drilling string is supported between a near bit stabilizer and a far bit stabilizer. A control stabilizer is located between the near and far bit stabilizers for applying a radial force to the drilling string within the control stabilizer such that a bend or curvature of the drilling string is produced between the near bit stabilizer and the far bit stabilizer. The control stabilizer is comprised of four bags located in the annular space between a housing of the control stabilizer and the drilling string for applying the radial force to the drilling string within the control stabilizer.
United Kingdom Patent Application No. GB 2,307,537 published May 28, 1997 by Astec Developments Limited describes a shaft alignment system for controlling the direction of rotary drilling. Specifically, a shaft, such as a drilling string, passes through a first shaft support means having a first longitudinal axis and a second shaft support means having a second longitudinal axis. The first and second shaft support means are rotatably coupled by bearing means having a bearing rotation axis aligned at a first non-zero angle with respect to the first longitudinal axis and aligned at a second non-zero angle with respect to the second longitudinal axis. As a result, relative rotation of the first and second shaft support means about their respective longitudinal axes varies the relative angular alignment of the first and second longitudinal axes.
The shaft passing through the shaft alignment system is thus caused to bend or curve in accordance with the relative angular alignment of the first and second longitudinal axes of the first and second shaft support means. The shaft may be formed as a unitary item with a flexible central section able to accommodate the desired curvature or it may be comprised of a coupling, such as a universal joint, to accommodate the desired curvature.
U.S. Pat. No. 5,685,379 issued Nov. 11, 1997 to Barr et. al., U.S. Pat. No. 5,706,905 issued Jan. 13, 1998 to Barr et. al. and U.S. Pat. No. 5,803,185 issued Sep. 8, 1998 to Barr et. al. describe a steerable rotary drilling system including a modulated bias unit, associated with the drilling bit, for applying a lateral bias to the drilling bit in a desired direction to control the direction of drilling. The bias unit is comprised of three equally spaced hydraulic actuators, each having a movable thrust member which is displaceable outwardly for engagement with the wellbore. The hydraulic actuators are operated in succession as the bias unit rotates during rotary drilling, each in the same rotational position, so as to displace the bias unit laterally in a selected direction.
PCT International Application No. PCT/US98/24012 published May 20, 1999 as No. WO 99/24688 by Telejet Technologies, Inc. describes the use of a stabilizer assembly for directional drilling. More particularly, a stabilizer sub is connected with the rotary drilling string such that the stabilizer sub remains substantially stationary relative to the wellbore as the drilling string rotates. The stabilizer sub includes a fixed upper stabilizer and an adjustable lower stabilizer. The lower adjustable stabilizer carries at least four stabilizer blades which are independently radially extendable from the body of the stabilizer sub for engagement with the wellbore.
Each stabilizer blade is actuated by a motor associated with each blade. Because each stabilizer blade is provided with its own motor, the stabilizer blades are independently extendable and retractable with respect to the body of the stabilizer sub. Accordingly, each blade may be selectively extended or retracted to provide for the desired drilling direction.
U.S. Pat. No. 5,307,885 issued May 3, 1994 to Kuwana et. al., U.S. Pat. No. 5,353,884 issued Oct. 11, 1994 to Misawa et. al. and U.S. Pat. No. 5,875,859 issued Mar. 2, 1999 to Ikeda et. al. all utilize harmonic drive mechanisms to drive rotational members supporting the drilling string eccentrically to deflect the drilling string and control the drilling direction.
More particularly, Kuwana et. al. describes a first rotational annular member connected with a first harmonic drive mechanism a spaced distance from a second rotational annular member connected with a second harmonic drive mechanism. Each rotational annular member has an eccentric hollow portion which rotates eccentrically around the rotational axis of the annular member. The drilling string is supported by the inner surfaces of the eccentric portions of the annular members. Upon rotation by the harmonic drive mechanisms, the eccentric hollow portions are rotated relative to each other in order to deflect the drilling string and change the orientation of the drilling string to the desired direction. Specifically, the orientation of the drilling string is defined by a straight line passing through the centres of the respective hollow portions of the annular members.
Misawa et. al. describes harmonic drive mechanisms for driving first and second rotatable annular members of a double eccentric mechanism. The first rotatable annular member defines a first eccentric inner circumferential surface. The second rotatable annular member, rotatably supported by the first eccentric inner circumferential surface of the first annular member, defines a second eccentric inner circumferential surface. The drilling string is supported by the second eccentric inner circumferential surface of the second annular member and uphole by a shaft retaining mechanism. Thus, upon actuation of the harmonic drive mechanisms, the first and second annular members are rotated resulting in the movement of the center of the second eccentric circumferential surface. Thus the drilling string is deflected from its rotational centre in order to orient it in the desired direction.
Upon deflection of the drilling string, the fulcrum point of the deflection of the drilling string tends to be located at the upper supporting mechanism, i.e. the upper shaft retaining mechanism. As a result, it has been found that the drilling string may be exposed to excessive bending stress.
Similarly, Ikeda et. al. describes harmonic drive mechanisms for driving first and second rotatable annular members of a double eccentric mechanism. However, Ikeda et. al. requires the use of a flexible joint, such as a universal joint, to be connected into the drilling string at the location at which the maximum bending stress on the drilling string takes place in order to prevent excessive bending stress on the drilling string. Thus, the flexible joint is located adjacent the upper supporting mechanism. Upon deflection of the drilling string by the double eccentric mechanism, the deflection is absorbed by the flexible joint and thus a bending force is not generated on the drilling string. Rather, the drilling string is caused to tilt downhole of the double eccentric mechanism. A fulcrum bearing downhole of the double eccentric mechanism functions as a thrust bearing and serves as a rotating centre for the lower portion of the drilling string to accommodate the tilting action.
However, it has been found that the use of a flexible or articulated shaft to avoid the generation of excessive bending force on the drilling string may not be preferred. Specifically, it has been found that the articulations of the flexible or articulated shaft may be prone to failure.
Thus, there remains a need in the industry for a steerable rotary drilling device or drilling direction control device for use with a rotary drilling string, and a method for use in rotary drilling for controlling the drilling direction, which provide relatively accurate control over the trajectory or orientation of the drilling bit during the drilling operation, while also avoiding the generation of excessive bending stress on the drilling string.
The present invention is directed at a drilling direction control device. The invention is also directed at methods of drilling utilizing a drilling direction control device and to methods for orienting a drilling system such as a rotary drilling system.
In an apparatus form of the invention the invention is comprised of a device which can be connected with a drilling string and which permits drilling to be conducted in a multitude of directions which deviate from the longitudinal axis of the drilling string, thus providing steering capability during drilling and control over the path of the resulting wellbore. Preferably, the device permits the amount of rate of change of the drilling direction to be infinitely variable between zero percent and 100 percent of the capacity of the device.
The device is comprised of a drilling shaft which is connectable with the drilling string and which is deflectable by bending to alter the direction of its longitudinal axis relative to the longitudinal axis of the drilling string and thus alter the direction of a drilling bit attached thereto. Preferably, the orientation of the deflection of the drilling shaft may be altered to alter the orientation of the drilling bit with respect to both the tool face and the magnitude of the deflection of the drilling bit or the bit tilt.
Preferably, the drilling shaft is deflectable between two radial supports. Preferably a length of the drilling shaft which is to be deflected is contained within a housing, which housing also encloses the radial supports.
The device is especially suited for use as part of a steerable rotary drilling system in which the drilling string and the drilling shaft are both rotated.
In one apparatus aspect of the invention, the invention is comprised of a drilling direction control device comprising:
(a) a rotatable drilling shaft;
(b) a housing for rotatably supporting a length of the drilling shaft for rotation therein; and
(c) a drilling shaft deflection assembly contained within the housing and axially located between a first support location and a second support location, for bending the drilling shaft between the first support location and the second support location, wherein the deflection assembly is comprised of:
(i) an outer ring which is rotatably supported on a circular inner peripheral surface of the housing and which has a circular inner peripheral surface that is eccentric with respect to the housing; and
(ii) an inner ring which is rotatably supported on the circular inner peripheral surface of the outer ring and which has a circular inner peripheral surface which engages the drilling shaft and which is eccentric with respect to the circular inner peripheral surface of the outer ring.
In other apparatus aspects of the invention, the invention is comprised of improvements in features of drilling direction control devices generally. These improvements may be used in conjunction with the drilling direction control device described above or may be used in conjunction with other drilling direction control devices.
The first support location and the second support location may be comprised of any structure which facilitates the bending of the drilling shaft therebetween and which permits rotation of the drilling shaft. Preferably the device is further comprised of a first radial bearing located at the first support location and a second radial bearing located at the second support location. Preferably the first radial bearing is comprised of a distal radial bearing, the first support location is comprised of a distal radial bearing location, the second radial bearing is comprised of a proximal radial bearing, and the second bearing location is comprised of a proximal radial bearing location.
The distal radial bearing may be comprised of any bearing, bushing or similar device which is capable of radially and rotatably supporting the drilling shaft while transmitting the effects of deflection of the drilling shaft past the distal radial bearing. For example, the distal radial bearing may allow for radial displacement of the drilling shaft. Preferably, however, the distal radial bearing is comprised of a fulcrum bearing which facilitates pivoting of the drilling shaft at the distal radial bearing location.
The proximal radial bearing may be comprised of any bearing, bushing or similar device which is capable of radially and rotatably supporting the drilling shaft. Preferably, the proximal radial bearing does not significantly transmit the effects of deflection of the drilling shaft past the proximal radial bearing so that the effects of deflection of the drilling shaft are confined to that portion of the device which is toward the distal end of the device from the proximal radial bearing. In the preferred embodiment, the proximal radial bearing is comprised of a cantilever bearing which restrains pivoting of the drilling shaft at the proximal radial bearing location.
The device preferably is further comprised of a distal seal at a distal end of the housing and a proximal seal at a proximal end of the housing, both of which are positioned radially between the housing and the drilling shaft to isolate and protect the radial bearings and the deflection assembly from debris. The seals are preferably positioned axially so that the deflection assembly is axially located between the distal and proximal ends of the housing, the distal radial bearing location is axially located between the distal end of the housing and the deflection assembly, and the proximal radial bearing location is axially located between the proximal end of the housing and the deflection assembly.
The seals may be comprised of any type of seal which is capable of withstanding relative movement between the housing and the drilling shaft as well as the high temperatures and pressures that are likely to be encountered during drilling. Preferably the seals are rotary seals to accommodate rotation of the drilling shaft relative to the housing. In the preferred embodiment, the seals are comprised of rotary seals which also accommodate lateral movement of the drilling shaft, are comprised of an internal wiper seal and an external barrier seal, and are lubricated with filtered lubricating fluid from within the housing.
The interior of the housing preferably defines a fluid chamber between the distal end and the proximal end, which fluid chamber is preferably filled with a lubricating fluid. The device preferably is further comprised of a pressure compensation system for balancing the pressure of the lubricating fluid contained in the fluid chamber with the ambient pressure outside of the housing.
The pressure compensation system may be comprised of any system which will achieve the desired balance of pressures, such as any system which allows communication between the ambient pressure outside of the housing and the lubricating fluid contained in the fluid chamber. In the preferred embodiment, the pressure compensation system is comprised of a pressure port on the housing.
The pressure compensation system is also preferably comprised of a supplementary pressure source for exerting pressure on the lubricating fluid so that the pressure of the lubricating fluid is maintained higher than the ambient pressure. Any mechanism which provides this supplementary pressure source may be used in the invention, which mechanism may be actuated hydraulically, pneumatically, mechanically or in any other manner.
In the preferred embodiment, the pressure compensation system includes the supplementary pressure source and is comprised of a balancing piston assembly, wherein the balancing piston assembly is comprised of a piston chamber defined by the interior of the housing and a movable piston contained within the piston chamber which separates the piston chamber into a fluid chamber side and a balancing side, wherein the fluid chamber side is connected with the fluid chamber, wherein the pressure port communicates with the balancing side of the piston chamber, and wherein the supplementary pressure source acts on the balancing side of the piston chamber. In the preferred embodiment, the supplementary pressure source is comprised of a biasing device which exerts a supplementary pressure on the piston, and the biasing device is comprised of a spring which is contained in the balancing side of the piston chamber.
The pressure compensation system is also preferably comprised of a lubricating fluid regulating system which facilitates charging of the fluid chamber with lubricating fluid and which provides adjustment during operation of the device of the amount of lubricating fluid contained in the fluid chamber in response to increased temperatures and pressures experienced by the lubricating fluid.
The lubricating fluid regulating system is preferably comprised of a relief valve which communicates with the fluid chamber and which permits efflux of lubricating fluid from the fluid chamber when the difference between the pressure of the lubricating fluid in the fluid chamber and the ambient pressure outside of the fluid chamber exceeds a predetermined relief valve pressure. This predetermined relief valve pressure is preferably equal to or slightly greater than the supplementary pressure exerted by the supplementary pressure source. In the preferred embodiment, where the supplementary pressure source is a spring, the predetermined relief valve pressure is set at slightly higher than the desired maximum amount of supplementary pressure to be exerted by the spring during operation of the device.
The distal seal and the proximal seal are both preferably lubricated with lubricating fluid from the fluid chamber. In order to reduce the risk of damage to the seals due to debris contained in the lubricating fluid, the seals are preferably each comprised of an internal wiper seal or internal isolation seal and a filtering mechanism for filtering the lubricating fluid from the fluid chamber before it encounters the seals so that the seals are isolated from the main volume of lubricating fluid contained within the fluid chamber and are lubricated with filtered lubricating fluid. Any type of filter capable of isolating the seals from debris having particles of the size likely to be encountered inside the fluid chamber may be used in the filtering mechanism.
The device is preferably further comprised of a device associated with the housing for restraining rotation of the housing. The rotation restraining device may be comprised of any apparatus which is capable of providing a restraining or anti-rotation function between the housing and a borehole wall during operation of the drilling direction control device.
The rotation restraining device or anti-rotation may be comprised of a single member extending from the housing. Preferably, the rotation restraining device is comprised of a plurality of members arranged about a circumference of the housing, each of which members are capable of protruding radially from the housing and are capable of engaging the borehole wall to perform the restraining or anti-rotation function.
In one preferred embodiment of the invention, the rotation restraining device is comprised of at least one roller on the housing, the roller having an axis of rotation substantially perpendicular to a longitudinal axis of the housing and being oriented such that it is capable of rolling about its axis of rotation in response to a force exerted on the roller substantially in the direction of the longitudinal axis of the housing.
Preferably the roller is comprised of a peripheral surface about its circumference and preferably the peripheral surface is comprised of an engagement surface for engaging a borehole wall. The engagement surface may be comprised of the peripheral surface of the roller being tapered.
The roller may be positioned on the housing at a fixed radial position extending from the housing, but preferably the roller is capable of movement between a retracted position and an extended position in which it extends from the housing. The rotation restraining device may be further comprised of a biasing device for biasing the roller toward the extended position, which biasing device may be comprised of any apparatus which can perform the biasing function. Preferably the biasing device is comprised of at least one spring which acts between the housing and the roller. Alternatively, the rotation restraining device may be comprised of an actuator for moving the roller between the retracted and extended positions.
Preferably the first preferred embodiment of rotation restraining device is comprised of a plurality of rollers spaced about a circumference of the housing. The plurality of rollers may be spaced about the circumference of the housing in any configuration. In the preferred embodiment of rotation restraining device comprising rollers, the rotation restraining device is comprised of three rotation restraining carriage assemblies spaced substantially evenly about the circumference of the housing, wherein each rotation restraining carriage assembly is comprised of three sets of rollers spaced axially along the housing, and wherein each set of rollers is comprised of four coaxial rollers spaced side to side.
In a second preferred embodiment of the invention, the rotation restraining device is comprised of at least one piston on the housing. The piston may be a fixed member which does not move radially relative to the housing. Preferably, the piston is capable of movement between a retracted position and an extended position in which it extends radially from the housing, in which case the rotation restraining device is preferably further comprised of an actuator device for moving the piston between the retracted and extended positions. The actuator device may be comprised of any apparatus which is capable of moving the piston radially relative to the housing. In the preferred embodiment, the actuator device is comprised of a hydraulic pump. Alternatively, the rotation restraining device may be comprised of a biasing device for biasing the piston toward the extended position.
Preferably the second preferred embodiment of rotation restraining device is comprised of a plurality of pistons spaced about a circumference of the housing. The plurality of pistons may be spaced about the circumference of the housing in any configuration. In the preferred embodiment of rotation restraining device comprising pistons, the rotation restraining device is comprised of three rotation restraining carriage assemblies spaced substantially evenly about the circumference of the housing, wherein each rotation restraining carriage assembly is comprised of a plurality of pistons spaced axially along the housing.
The device is preferably further comprised of a distal thrust bearing contained within the housing for rotatably supporting the drilling shaft axially at a distal thrust bearing location and a proximal thrust bearing contained within the housing for rotatably supporting the drilling shaft axially at a proximal thrust bearing location. The thrust bearings may be comprised of any bearing, bushing or similar device which is capable of axially and rotatably supporting the drilling shaft.
The thrust bearings may be located at any axial positions on the device in order to distribute axial loads exerted on the device between the drilling shaft and the housing. Preferably the thrust bearings also isolate the deflection assembly from axial loads exerted through the device. As a result, the distal thrust bearing location is preferably located axially between the distal end of the housing and the deflection assembly, and the proximal thrust bearing location is preferably located axially between the proximal end of the housing and the deflection assembly. This configuration permits the thrust bearings to be lubricated with lubricating fluid from the fluid chamber.
Preferably the proximal thrust bearing location is located axially between the proximal end of the housing and the proximal radial bearing location. This configuration simplifies the design of the proximal thrust bearing location, particularly where the proximal radial bearing is comprised of a cantilever bearing and the proximal thrust bearing is thus isolated from the effects of deflection of the drilling shaft. The proximal thrust bearing may also be located at the proximal radial bearing location so that the proximal radial bearing is comprised of the proximal thrust bearing.
Preferably, the distal thrust bearing is comprised of the fulcrum bearing so that the distal thrust bearing location is at the distal radial bearing location. The fulcrum bearing may in such circumstances be comprised of any configuration of bearings, bushings or similar devices which enables the fulcrum bearing to function as both a radial bearing and a thrust bearing while continuing to permit the effects of deflection of the drilling shaft to be transmitted past the fulcrum bearing.
In the preferred embodiment, the fulcrum bearing is preferably comprised of a fulcrum bearing assembly, wherein the fulcrum bearing assembly is preferably comprised of at least one row of spherical thrust bearings positioned at first axial position, at least one row of spherical thrust bearings positioned at a second axial position and at least one row of spherical radial bearings positioned at a third axial position, wherein the third axial position is located between the first and second axial positions. Preferably the spherical thrust bearings and the spherical radial bearings are arranged substantially about a common center of rotation.
The thrust bearings are preferably maintained in a preloaded condition in order to minimize the likelihood of relative axial movement during operation of the device between the drilling shaft and the housing. The radial bearings may also be preloaded to minimize the likelihood of relative radial movement during operation of the device between the drilling shaft and the housing. In the preferred embodiment, the proximal thrust bearing and the fulcrum bearing are both preloaded.
The thrust bearings may be preloaded in any manner. Preferably the apparatus for preloading the bearings provides for adjustment of the amount of preloading to accommodate different operating conditions for the device.
In the preferred embodiment, the thrust bearings are preloaded. As a result, in the preferred embodiment the device is further comprised of a distal thrust bearing preload assembly and a proximal thrust bearing preload assembly. In the preferred embodiment, each thrust bearing preload assembly is comprised of a thrust bearing shoulder and a thrust bearing collar, between which a thrust bearing is axially maintained. The thrust bearing collar is axially adjustable to preload the thrust bearing and to adjust the amount of preloading. In the preferred embodiment, the thrust bearing collar is threaded onto the housing and is axially adjustable by rotation relative to the housing.
In order to reduce the likelihood of a thrust bearing collar becoming loosened by axial movement during operation of the device, the device is preferably further comprised of a distal thrust bearing retainer for retaining the distal thrust bearing in position without increasing the preloading on the distal thrust bearing, and is further comprised of a proximal thrust bearing retainer for retaining the proximal thrust bearing in position without increasing the preloading on the proximal thrust bearing.
The thrust bearing retainers may be comprised of any apparatus which functions to maintain the desired axial position of the thrust bearing collars without applying an additional compressive load to the thrust bearings. Preferably this result is achieved by retaining the thrust bearing collars against axial movement with a compressive force which is not applied to the thrust bearings.
In the preferred embodiment, each thrust bearing retainer is comprised of a locking ring slidably mounted on the thrust bearing collar to a position in which it abuts the housing and a locking ring collar which can be tightened against the locking ring to hold the locking ring in position between the housing and the locking ring collar. Alternatively, the locking ring may be adapted to abut some component of the device other than the housing as long as the force exerted by the tightening of the locking ring collar is not borne by the thrust bearing.
In the preferred embodiment, the thrust bearing collar is threaded for adjustment by rotation and the locking ring is mounted on the thrust bearing collar such that the locking ring does not rotate relative to the thrust bearing collar. Preferably, the apparatus for mounting the locking ring on the thrust bearing collar is comprised of a key on one and an axially oriented slot on the other of the locking ring and the thrust bearing collar. Any other suitable mounting apparatus may, however, be used.
The locking ring may be held abutted against the housing or other component of the device by the frictional forces resulting from the tightening of the locking ring collar. In the preferred embodiment, the locking ring is comprised of a housing abutment surface, the housing is comprised of a complementary locking ring abutment surface, and engagement of the housing abutment surface and the locking ring abutment surface prevents rotation of the locking ring relative to the housing. In the preferred embodiment, the abutment surfaces are comprised of complementary teeth.
In operation of the thrust bearing preload assembly and the thrust bearing retainer, the amount of thrust bearing preload is established by rotating the thrust bearing collar to establish a suitable axial load representing the desired amount of preloading on the thrust bearing. The locking ring is then slid over the thrust bearing collar until it abuts the housing and the complementary abutment surfaces are engaged and the locking ring collar is then tightened against the locking ring to hold the locking ring in position between the housing and the locking ring collar at a desired torque load.
The deflection assembly may be actuated by any mechanism or mechanisms which are capable of independently rotating the outer ring and the inner ring. The actuating mechanism may be independently powered, but in the preferred embodiment the actuating mechanism utilizes rotation of the drilling shaft as a source of power to effect rotation of the outer ring and the inner ring.
Preferably, the deflection assembly is further comprised of an outer ring drive mechanism for rotating the outer ring using rotation of the drilling shaft and a substantially identical inner ring drive mechanism for rotating the inner ring using rotation of the drilling shaft. Preferably, the inner and outer rings are rotated in a direction opposite to the direction of rotation of the drilling string and thus opposite to a direction of rotation of slippage of the non-rotating portion of the device (20), being the housing (46).
In the preferred embodiment, each drive mechanism is comprised of a clutch for selectively engaging and disengaging the drilling shaft from the ring, wherein the clutch is comprised of a pair of clutch plates which are separated by a clutch gap when the clutch is disengaged. Preferably, each clutch may also function as a brake for the inner and outer rings when the clutch plates are disengaged.
Each clutch is further comprised of a clutch adjustment mechanism for adjusting the clutch gap. Any mechanism facilitating the adjustment of the clutch gap may be used for the clutch adjustment mechanism.
Preferably, each clutch adjustment mechanism is comprised of a clutch adjustment member associated with one of the pair of clutch plates such that movement of the clutch adjustment member will result in corresponding movement of the clutch plate, a first guide for guiding the clutch adjustment member for movement in a first direction, and a movable key associated with the clutch adjustment member, the key comprising a second guide for urging the clutch adjustment member in a second direction, which second direction has a component parallel to the first guide and has a component perpendicular to the first guide.
The first guide may be comprised of any structure which is capable of guiding the clutch adjustment member for movement in the first direction. Similarly, the second guide may be comprised of any structure which is capable of urging the clutch adjustment member in the second direction.
The clutch adjustment member, the key and the clutch plate are preferably associated with each other such that the key effects movement of the clutch adjustment member which in turn effects movement of the clutch plate to increase or decrease the clutch gap. The clutch adjustment member may therefore be rigidly attached to or integrally formed with one of the key or the clutch plate, but should be capable of some movement relative to the other of the key and the clutch plate.
The function of the first guide is to enable the key and the clutch plate to move relative to each other without imparting a significant force to the clutch plate tending to rotate the clutch plate. In other words, the movement of the key in the second direction is converted through the apparatus of the key, the clutch adjustment member, the first guide and the clutch plate into movement of the clutch plate in a direction necessary to increase or decrease the clutch gap.
In the preferred embodiment, the first guide is comprised of a first slot which extends circumferentially in the clutch plate and thus perpendicular to a direction of movement of the clutch plate necessary to increase or decrease the clutch gap, the clutch adjustment member is fixed to the key, and the clutch adjustment member engages the first slot. Preferably, the second guide is comprised of a surface which urges the key to move in the second direction in response to a force applied to the key. In the preferred embodiment, the surface is comprised in part of a key ramp surface which is oriented in the second direction.
In the preferred embodiment, the dutch adjustment mechanism is further comprised of a clutch adjustment control mechanism for controlling the movement of the key. This clutch adjustment control mechanism may be comprised of any apparatus, but in the preferred embodiment is comprised of an adjustment screw which is connected to the key and which can be rotated inside a threaded bore to finely control the movement of the key.
In the preferred embodiment, the clutch adjustment mechanism is further comprised of a clutch adjustment locking mechanism for fixing the position of the key so that the clutch gap can be maintained at a desired setting. This clutch adjustment locking mechanism may be comprised of any apparatus, but in the preferred embodiment is comprised of one or more set screws associated with the clutch adjustment member which can be tightened to fix the position of the key once the desired clutch gap setting is achieved.
Preferably the clutch adjustment control mechanism controls movement of the key in a direction that is substantially perpendicular to the longitudinal axis of the device. As a result, the second guide preferably converts movement of the key in a direction substantially perpendicular to the longitudinal axis of the device to movement of the key in the second direction.
In the preferred embodiment, the key is positioned in a cavity defined by the ring drive mechanism. In addition, in the preferred embodiment the key is comprised of a key ramp surface oriented in the second direction and the cavity defines a complementary cavity ramp surface, so that movement of the key by the clutch adjustment control mechanism in a direction that is substantially perpendicular to the longitudinal axis of the device results in the key moving along the cavity ramp surface in the second direction, which in turn causes the clutch adjustment member to move in the second direction.
The component of movement of the key along the cavity ramp surface which is parallel to the first slot results in the clutch adjustment member moving in the first slot without imparting a significant rotational force to the clutch plate. The component of movement of the key along the cavity ramp surface which is perpendicular to the first slot results in an increase or decrease in the clutch gap by engagement of the clutch adjustment member with the clutch plate.
Alternatively, the clutch adjustment member may be fixed to the clutch plate so that the clutch adjustment member does not move relative to the clutch plate. In this second embodiment of clutch adjustment mechanism, the first guide is preferably comprised of a first slot which is oriented in a direction that is parallel to a direction of movement necessary to increase or decrease the clutch gap and is positioned between the key and the clutch plate so that the clutch adjustment member moves in the first guide. The second guide in this embodiment is preferably comprised of a second slot in the key which crosses the first slot so that the clutch adjustment member simultaneously engages both the first slot and the second slot.
In the second embodiment of clutch adjustment mechanism, the key may not include the key ramp surface, in which case the second slot is preferably oriented in the second direction. Alternatively, the key may include the key ramp surface, in which case the second slot is preferably oriented in the second direction.
The device is preferably incorporated into a drilling string by connecting the drilling shaft with the drilling string. In order that rotation of the drilling string will result in rotation of the drilling shaft, the device is further comprised of a drive connection for connecting the drilling shaft with the drilling string.
The drive connection may be comprised of any apparatus which is capable of transmitting torque from the drilling string to the drilling shaft. Preferably, the drive connection is sufficiently tight between the drilling string and the drilling shaft so that the drive connection is substantially xe2x80x9cbacklash-freexe2x80x9d.
In the preferred embodiment, the drive connection is comprised of a tolerance assimilation sleeve which is interspersed between the drilling shaft and the drilling string. In the preferred embodiment, the drive connection is further comprised of a first drive profile on the drilling shaft and a complementary second drive profile on the drilling string and the tolerance assimilation sleeve is positioned between the first drive profile and the second drive profile in order to reduce the tolerance between the first drive profile and the second drive profile.
The first and second drive profiles may be comprised of any complementary configurations which facilitate the transmission of torque between the drilling string and the drilling shaft. In the preferred embodiment, the first and second drive profiles are comprised of octagonal profiles and the tolerance assimilation sleeve includes compatible octagonal profiles. The tolerance assimilation sleeve thus absorbs or assimilates some of the tolerance between the octagonal profile on the drilling shaft and the complementary octagonal profile on the drilling string in order to make the transmission of torque between the drilling string and the drilling shaft more smooth and substantially xe2x80x9cbacklash-freexe2x80x9d.
In the preferred embodiment, the effectiveness of the tolerance assimilation sleeve is further enhanced by the sleeve being comprised of a material having a thermal expansion rate higher than the thermal expansion rate of the drilling string, so that the tolerance assimilation sleeve will absorb or assimilate more tolerance between the drilling shaft and the drilling string as the device is exposed to increasing temperatures during its operation. In the preferred embodiment, the tolerance assimilation sleeve is comprised of a beryllium copper alloy.
The deflection assembly is preferably actuated to orient the outer ring and the inner ring relative to a reference orientation so that the device may be used to provide directional control during drilling operations.
Preferably, the deflection assembly is actuated with reference to the orientation of the housing, which is preferably restrained from rotating during operation of the device by the rotation restraining device. As a result, the device is preferably further comprised of a housing orientation sensor apparatus associated with the housing for sensing the orientation of the housing.
The housing orientation sensor apparatus preferably senses the orientation of the housing in three dimensions in space and may be comprised of any apparatus which is capable of providing this sensing function and the desired accuracy in sensing. Preferably the housing orientation sensor apparatus is comprised of one or more magnetometers, accelerometers or a combination of both types of sensing apparatus.
The housing orientation sensing apparatus is preferably located as dose as possible to the distal end of the housing so that the sensed orientation of the housing will be as close as possible to the distal end of the borehole during operation of the device. In the preferred embodiment, the housing orientation sensor apparatus is contained in an at-bit-inclination (ABI) insert which is located inside the housing axially between the distal radial bearing and the deflection assembly.
The device is also preferably further comprised of a deflection assembly orientation sensor apparatus associated with the deflection assembly for sensing the orientation of the deflection assembly.
The deflection assembly orientation sensor apparatus may provide for sensing of the orientation of the outer ring and the inner ring in three dimensions in space, in which case the deflection assembly orientation sensor apparatus may be comprised of an apparatus similar to that of the housing orientation sensor apparatus and may even eliminate the need for the housing orientation sensor apparatus.
Preferably, however the deflection assembly orientation sensor apparatus senses the orientation of both the outer ring and the inner ring of the deflection assembly relative to the housing and may be comprised of any apparatus which is capable of providing this sensing function and the desired accuracy in sensing. The deflection assembly orientation sensor apparatus may be comprised of one sensor which senses the resultant orientation of the inner peripheral surface of the inner ring relative to the housing.
In the preferred embodiment, the deflection assembly orientation sensor apparatus is comprised of separate sensor apparatus for sensing the orientation of each of the outer ring and the inner ring relative to the housing. In the preferred embodiment, these sensor apparatus are comprised of a plurality of magnets associated with each of the drive mechanisms which rotate with components of the drive mechanism. The magnetic fields generated by these magnets are then sensed by a stationary counter device associated with a non-rotating component of the drive mechanism to sense how far the rings rotate from a reference or home position.
The deflection assembly orientation sensor apparatus may be further comprised of one or more high speed position sensors associated with each drive mechanism, for sensing the rotation which is actually transmitted from the drilling shaft through the clutch to the drive mechanism. The high speed position sensors may be associated with an rpm sensor which in turn is associated with the drilling shaft for sensing the rotation of the drilling shaft. A comparison of the rotation sensed by the high speed position sensors and the rotation sensed by the rpm sensor may be used to determine slippage through the dutch and detect possible malfunctioning of the clutch.
The deflection assembly is preferably actuated with reference to the orientation of both the housing and the deflection assembly, since the housing orientation sensor apparatus preferably senses the orientation of the housing in space while the deflection assembly orientation sensor apparatus preferably senses the orientation of the outer ring and the inner ring relative to the housing.
The deflection assembly may be actuated by manipulating the deflection assembly using any device or apparatus which is capable of rotating the outer and inner rings. Preferably, however the device is further comprised of a controller for. controlling the actuation of the deflection assembly. Preferably, the controller is operatively connected with both the housing orientation sensor apparatus and the deflection assembly orientation sensor apparatus so that the deflection assembly may be actuated by the controller with reference to the orientation of both the housing and the deflection assembly.
The controller may be positioned at any location at which it is capable of performing the controlling function. The controller may therefore be positioned a between the proximal and distal ends of the housing, along the drilling string, or may even be located outside of the borehole. In the preferred embodiment, the controller is located in an electronics insert which is positioned axially between the proximal radial bearing and the deflection assembly.
One of the features of the preferred embodiment of the invention is that the device is preferably compatible with drilling string communication systems which facilitate the transmission of data from or to downhole locations. Such communication systems often include sensors for sensing parameters such as the orientation of the drilling string. Preferably the device is capable of processing data received from sensors associated with such drilling string communication systems in order to control the actuation of the deflection assembly.
Preferably the device is operated by connecting a drilling string communication system with the device so that a drilling string orientation sensor apparatus is operatively connected with the device and the deflection assembly may be actuated with reference to the orientation of the drilling string. By considering the orientation of the drilling string, the orientation of the housing and the orientation of the deflection assembly relative to the housing, and by establishing a relationship linking the three orientations, the deflection assembly may be actuated to reflect a desired orientation of the drilling string once data pertaining to the desired orientation of the drilling string has been processed by the device to provide instructions for actuation of the deflection assembly.
This relationship linking the three orientations may be established in any manner. In the preferred embodiment the relationship is established by providing reference positions for each of the housing orientation sensor apparatus, the deflection assembly orientation sensor apparatus and the drilling string orientation sensor apparatus which can be related to one another.
The deflection assembly may be actuated indirectly by the device converting data pertaining to the orientation of the drilling string or some other parameter or the deflection assembly may be actuated directly by the device receiving instructions specifically pertaining to the actuation of the deflection assembly. Preferably, however the controller is connectable with a drilling string orientation sensor apparatus so that the deflection assembly may be actuated indirectly by the device converting data pertaining to the orientation of the drilling string.
This configuration simplifies the operation of the device, since an operator of the device need only establish a desired orientation of the drilling string through communication with the drilling string communication system. The drilling string communication system can then provide instructions to the device in the form of data pertaining to the desired orientation of the drilling string which the device will then process having regard to the orientation of the housing and the orientation of the deflection assembly relative to the housing in order to actuate the deflection assembly to reflect the desired orientation of the drilling string. Preferably the data is processed by the controller of the device.
The device may be further comprised of a device memory for storing data downloaded to control the operation of the device, data generated by the housing orientation sensor apparatus, the deflection assembly orientation sensor apparatus, the drilling string orientation sensor apparatus, or data obtained from some other source such as, for example an operator of the device. The device memory is preferably associated with the controller, but may be positioned anywhere between the proximal and distal ends of the housing, along the drilling string, or may even be located outside of the borehole. During operation of the device, data may be retrieved from the device memory as needed in order to control the operation of the device, including the actuation of the deflection assembly.
In the preferred embodiment the housing orientation sensor apparatus, the deflection assembly orientation sensor apparatus, the drilling string orientation sensor apparatus and the controller all transmit electrical signals between various components of the device and the drilling string, including the deflection assembly, the controller and the drilling string communication system.
In order to transmit electrical signals from the housing to the drilling shaft, and thus the drilling string communication system, it is necessary in the preferred embodiment to transmit these signals between two components which are rotating relative to each other, which may render conventional electrical circuits impractical for this purpose.
These signals may be transmitted between the components by any direct or indirect coupling or communication method or any mechanism, structure or device for directly or indirectly coupling the components which are rotating relative to each other. For instance, the signals may be transmitted by a slip ring or a gamma-at-bit communication toroid coupler. However, in the preferred embodiment, the signals are transmitted by an electromagnetic coupling device.
As a result, in the preferred embodiment, the device is further comprised of an electromagnetic coupling device associated with the housing and the drilling shaft for electrically connecting the drilling shaft and the housing.
This electromagnetic coupling device is preferably comprised of a housing conductor positioned on the housing and a drilling shaft conductor positioned on the drilling shaft, wherein the housing conductor and the drilling shaft conductor are positioned sufficiently dose to each other so that electrical signals may be induced between them. The conductors may be single wires or coils and may either be wrapped or not wrapped around magnetically permeable cores.
The invention is also comprised of methods for orienting a drilling system, which methods are particularly suited for orienting a rotary drilling system. The methods may be performed manually or on a fully automated or semi-automated basis.
The methods may be performed manually by having an operator provide instructions to the drilling direction control device. The methods may be performed fully automatically or semi-automatically by having a drilling string communication system provide instructions to the drilling direction control device.
As described above with respect to the apparatus embodiments, one of the features of the preferred embodiment of the invention is that the invention may be used in conjunction with drilling string communication systems and is capable of interfacing with such systems.
For example, the invention may be used in conjunction with a measurement-while-drilling (MWD) apparatus which may be incorporated into a drilling string for insertion in a borehole as part of an MWD system. In an MWD system, sensors associated with the MWD apparatus provide data to the MWD apparatus for communication up the drilling string to an operator of the drilling system. These sensors typically provide directional information about the borehole being drilled by sensing the orientation of the drilling string so that the operator can monitor the orientation of the drilling string in response to data received from the MWD apparatus and adjust the orientation of the drilling string in response to such data. An MWD system also typically enables the communication of data from the operator of the system down the borehole to the MWD apparatus.
Preferably, the drilling direction control device of the invention is capable of communicating with the MWD system or other drilling string communication system so that data concerning the orientation of the drilling string can be received by the device. Preferably, the drilling direction control device is also capable of processing data received from the drilling string communication system pertaining to the orientation of the drilling string in order to generate instructions for actuation of the deflection assembly.
In other words, preferably the drilling direction control device communicates with the drilling string communication system and not directly with the operator of the drilling system. In addition, preferably the drilling direction control device is capable of interfacing with the drilling string communication system such that it can process data received from the communication system.
This will allow the operator of the drilling system to be concerned primarily with the orientation of the drilling string during drilling operations, since the drilling direction control device will interface with the drilling string communication system and adjust the deflection assembly with reference to the orientation of the drilling string. This is made possible by establishing a relationship amongst the orientation of the drilling string, the orientation of the housing and the orientation of the deflection assembly, thus simplifying drilling operations.
Establishing a communication link between the drilling direction control device and the drilling string communication system facilitates the operation of the drilling direction control device on a fully automated or semi-automated basis with reference to the orientation of the drilling string. The device may also be operated using a combination of manual, fully automated and semi-automated methods, and may be assisted by expert systems and artificial intelligence (AI) to address actual drilling conditions that are different from the expected drilling conditions.
Operation of the drilling direction control device on a fully automated basis involves preprogramming the device with a desired actuation of the device or with a series of desired actuations of the device. The device may then be operated in conjunction with the drilling string communication system to effect drilling for a preprogrammed duration at one desired orientation of the drilling string, followed by drilling for a preprogrammed duration at a second desired orientation of the drilling string, and so on. The device may be programmed indirectly with data pertaining to the desired orientation of the drilling string or programmed directly with specific instructions pertaining to the actuation of the device. Preferably the programming is performed indirectly and the device processes the data to generate instructions for actuating the device.
Operation of the drilling direction control device on a semi-automated basis involves establishing a desired actuation of the device before the commencement of drilling operations and actuating the deflection assembly to deflect the drilling shaft to reflect the desired actuation. This desired actuation is then maintained until a new desired actuation is established and will typically require temporary cessation of drilling to permit the deflection assembly to be actuated to reflect the new desired actuation of the device. The desired actuation of the device may be established indirectly by providing the device with data pertaining to the desired orientation of the drilling string or may be established directly by providing the device with specific instructions pertaining to actuation of the device. Preferably the desired actuation of the device is given indirectly and the device processes the data to generate instructions for actuating the device.
Operation of the drilling direction control device may also involve maintaining the deflection of the drilling shaft during drilling operations so that the deflection of the drilling shaft continues to reflect the desired actuation of the device. In the preferred embodiment, the maintaining step may be necessary where some rotation of the housing is experienced during drilling operations and may involve adjusting the actuation of the deflection assembly to account for rotational displacement of the housing, since the deflection assembly in the preferred embodiment is actuated relative to the housing. The actuation of the deflection assembly may also require adjusting to account for undesired slippage of the clutch or clutch/brake comprising the drive mechanisms of the inner and outer rings of the deflection assembly.
The maintaining step may be performed manually by an operator providing instructions to the device to adjust the deflection of the drilling shaft. Preferably, however, the maintaining step is automated so that the drilling string communication system provides instructions to the device to adjust the deflection of the drilling shaft. These instructions may be given indirectly by providing the device with data pertaining to the orientation of the drilling string or may be given directly by providing the device with specific instructions for actuating the device to adjust the deflection of the drilling shaft. Preferably the instructions are given indirectly and the device processes the data to generate instructions for actuating the device.
As a result, in one method aspect of the invention, the invention is comprised of a method for orienting a rotary drilling system, the rotary drilling system being comprised of a rotatable drilling string, a drilling string communication system and a drilling direction control device, the drilling direction control device comprising a deflectable drilling shaft connected with the drilling string, the method comprising the following steps:
(a) orienting the drilling string at a desired orientation;
(b) sensing the desired orientation of the drilling string with the drilling string communication system;
(c) communicating the desired orientation of the drilling string to the drilling direction control device; and
(d) actuating the drilling direction control device to deflect the drilling shaft to reflect the desired orientation.
Preferably the drilling direction control device is actuated to reflect the desired orientation by actuating the device to account for the relative positions of the drilling string and the actuating apparatus. In a preferred embodiment, the drilling direction control device is further comprised of a housing and a deflection assembly, and the drilling direction control device is actuated to reflect the desired orientation of the device by accounting for the relative positions of the drilling string, the housing and the deflection assembly.
The drilling direction control device may be actuated in any manner and may be powered separately from the rotary drilling system. In the preferred embodiment, the drilling direction control device is actuated by rotation of the drilling string and the actuating step is comprised of rotating the drilling string.
The orienting step may be comprised of communicating the desired orientation of the drilling string directly from the surface of the wellbore to the drilling direction control device either with or without manipulating the drilling string. Preferably, however, the orienting step is comprised of comparing a current orientation of the drilling string with the desired orientation of the drilling string and rotating the drilling string to eliminate any discrepancy between the current orientation and the desired orientation. Once the desired orientation of the drilling string is achieved by manipulation of the drilling string, the desired orientation may then be communicated to the drilling direction control device either directly from the surface of the wellbore or from a drilling string orientation sensor located somewhere on the drilling string.
The method may also be comprised of the further step of periodically communicating the current orientation of the drilling string to the drilling direction control device. Preferably, the current orientation of the drilling string is periodically communicated to the drilling direction control device after a predetermined delay.
The step of communicating the desired orientation of the drilling string to the drilling direction control device may be comprised of communicating the desired orientation of the drilling string from the drilling string communication system to the drilling direction control device and the step of periodically communicating the current orientation of the drilling string to the drilling direction control device may be comprised of periodically communicating the current orientation of the drilling string from the drilling string communication system to the drilling direction control device.
The actuating step may be comprised of waiting for a period of time equal to or greater than the predetermined delay once the drilling string is oriented at the desired orientation so that the desired orientation of the drilling string is communicated to the drilling direction control device and rotating the drilling string to actuate the drilling direction control device to reflect the desired orientation of the drilling string.
The drilling direction control device may be further comprised of a device memory, in which case the method may be further comprised of the step of storing the current orientation of the drilling string in the device memory when it is communicated to the drilling direction control device.
Where the drilling direction control device is further comprised of a device memory, the actuating step may be further comprised of the steps of retrieving from the device memory the desired orientation of the drilling string and rotating the drilling string to actuate the drilling direction control device to reflect the desired orientation of the drilling string.
The method may be further comprised of the step of maintaining the deflection of the drilling shaft to reflect the desired orientation of the drilling shaft during operation of the rotary drilling system. The orientation maintaining step may be comprised of the steps of communicating the current orientation of the drilling string from the drilling string communication system to the drilling direction control device and actuating the drilling direction control device to reflect the desired orientation of the drilling string and the current orientation of the drilling shaft.
In a second method aspect of the invention, the invention is comprised of a method for orienting a rotary drilling system, the rotary drilling system being comprised of a rotatable drilling string, a drilling string communication system and a drilling direction control device, the drilling direction control device comprising a deflectable drilling shaft connected with the drilling string, the method comprising the following steps:
(a) communicating a desired orientation of the drilling string to the drilling direction control device; and
(b) actuating the drilling direction control device to deflect the drilling shaft to reflect the desired orientation.
Preferably the drilling direction control device is actuated to reflect the desired orientation by actuating the device to account for the relative positions of the drilling string and the actuating apparatus. In a preferred embodiment, the drilling direction control device is further comprised of a housing and a deflection assembly, and the drilling direction control device is actuated to reflect the desired orientation of the device by accounting for the relative positions of the drilling string, the housing and the deflection assembly.
The drilling direction control device may be actuated in any manner and may be powered separately from the rotary drilling system. In the preferred embodiment, the drilling direction control device is actuated by rotation of the drilling string and the actuating step is comprised of rotating the drilling string.
The method may also be comprised of the further step of periodically communicating the current orientation of the drilling string to the drilling direction control device. Preferably, the current orientation of the drilling string is periodically communicated to the drilling direction control device after a predetermined delay.
The step of communicating the desired orientation of the drilling string to the drilling direction control device may be comprised of communicating the desired orientation of the drilling string from the drilling string communication system to the drilling direction control device and the step of periodically communicating the current orientation of the drilling string to the drilling direction control device may be comprised of periodically communicating the current orientation of the drilling string from the drilling string communication system to the drilling direction control device.
The actuating step may be comprised of waiting for a period of time less than the predetermined delay so that the current orientation of the drilling string is not communicated to the drilling direction control device and rotating the drilling string to actuate the drilling direction control device to reflect the desired orientation of the drilling string.
The drilling direction control device may be further comprised of a device memory, in which case the method may be further comprised of the step of storing the desired orientation of the drilling string in the device memory when it is communicated to the drilling direction control device.
Where the drilling direction control device is further comprised of a device memory, the actuating step may be further comprised of the steps of retrieving from the device memory the desired orientation of the drilling string and rotating the drilling string to actuate the drilling direction control device to reflect the desired orientation of the drilling string.
The method may be further comprised of the step of maintaining the deflection of the drilling shaft to reflect the desired orientation of the drilling shaft during operation of the rotary drilling system. The orientation maintaining step may be comprised of the steps of communicating the current orientation of the drilling string from the drilling string communication system to the drilling direction control device and actuating the drilling direction control device to reflect the desired orientation of the drilling string and the current orientation of the drilling shaft.
In a third method aspect of the invention, the invention is comprised of a method for orienting a rotary drilling system, the rotary drilling system being comprised of a rotatable drilling string, a drilling string communication system, and a drilling direction control device, the drilling direction control device comprising a deflectable drilling shaft connected with the drilling string, the method comprising the following steps:
(a) determining a desired orientation of the rotary drilling system;
(b) communicating the desired orientation of the rotary drilling system from the drilling string communication system to the drilling direction control device; and
(c) actuating the drilling direction control device to deflect the drilling shaft to reflect the desired orientation of the rotary drilling system.
The drilling direction control device may be further comprised of a device memory, in which case the method may be further comprised of the step of storing the desired orientation of the rotary drilling system in the device memory when it is communicated to the drilling direction control device.
Where the drilling direction control device is further comprised of a device memory, the actuating step may be further comprised of the steps of retrieving from the device memory the desired orientation of the rotary drilling system and rotating the drilling string to actuate the drilling direction control device to reflect the desired orientation of the rotary drilling system.
The method may be further comprised of the step of maintaining the desired orientation of the rotary drilling system during operation of the rotary drilling system. The orientation maintaining step may be comprised of the steps of communicating the current orientation of the rotary drilling system from the drilling string communication system to the drilling direction control device and actuating the drilling direction control device to reflect the desired orientation of the rotary drilling system and the current orientation of the drilling shaft.
In any of the method aspects of the invention, the drilling direction control device may be further comprised of a housing for rotatably supporting the drilling shaft and the orientation maintaining step may be comprised of adjusting the deflection of the drilling shaft to account for rotation of the housing during drilling operations.
In addition, the drilling direction control device is preferably equipped to respond to basic default instructions concerning the magnitude of deflection of the drilling shaft. For example, the device is preferably equipped to provide for a zero deflection mode where the inner and outer rings are oriented opposite to each other to provide for no deflection of the drilling shaft and a full deflection mode where the deflection of the drilling shaft is a maximum predetermined amount, which predetermined amount may be equal to or less than the maximum deflection permitted by the deflection assembly. The device may also be equipped to respond to a plurality of default instructions such as zero deflection, full deflection and numerous magnitudes of deflection in between.
Where the device is in zero deflection mode, drilling is performed without altering the drilling direction. In other words, drilling is permitted to proceed in a substantially straight direction. The zero deflection mode also permits the device to be run into and out of the wellbore.